Conventional fluorescent lighting assemblies employ ballasts that are connected to opposite ends of fluorescent lamps. For preheat or rapid-start fluorescent lamps, the ballast is connected in series with the two pins and the filaments at opposite ends of the lamp when the starter switch is closed. When the starter switch is opened the ballast reactor produces a high voltage between filaments at opposite ends of the lamp striking an arc through the argon and mercury vapor in the lamp.
For an instant start fluorescent lamp, no starter switch is used. The circuit is arranged so that a high voltage will be impressed across the lamp when the lamp circuit is closed and the voltage across the lamp is reduced to its normal operating value as soon as conduction takes place and the lamp is started.
In each case the ballast is connected to the bases at both ends of the fluorescent lamp. At least one commercially available instant start ballast is capable of operating multiple lamps in which the ballast is connected only to the pins or electrodes at one lamp end. Interior pins on adjacent lamp bases are commoned. The MULTILITE MUL120 manufactured and sold by Electrofab, Ltd. is capable of energizing an eight foot instant start fluorescent lamp or two four foot instant start fluorescent lamps with adjacent pins on adjacent lamp bases commoned.
For conventional ballasts used in overhead troffers or luminaires, the ballast or ballasts are mounted at the center of the troffer and attached to the top of the troffer. Wires extend from the ballast or ballasts to sockets located at opposite ends of the troffer. For a four lamp assembly, wires must be connected to sockets at both ends of the four lamps. When a defective ballast is replaced, often on a trial and error basis, these wires must be disconnected and reconnected. Installation and maintenance of conventional lighting assemblies is therefor time consuming and cost is added to the manufacturing cost of the lighting assembly.
The commercially available Electrofab MULTILITE MUL120 ballast is housed in a standard ballast case and is also attached in the center of a troffer with wire leads extending from the ballast case to fluorescent lamp sockets at one end of the troffer. This prior art ballast must still be wired in place, and it differs from other conventional ballasts only in that the external electrical wire leads, having a length of up to three feet, are wired just to one end of the lighting fixture. The wiring assembly is therefore no simpler than conventional wiring assemblies in which wires are connected to sockets at opposite ends of the lighting assembly.
One approach to simplifying and therefore reducing the cost of ballast installation is disclosed in U.S. patent application Ser. No. 08/309,300 filed Sep. 20, 1994, now abandoned assigned to The Whitaker Corporation. An integral ballast that can be mounted at one end of a lighting assembly is disclosed in that application. However, a neutral wire must still be connected to the opposite end of the lighting assembly and this wiring must be completed during assembly of the lighting fixture.